The option -f specifies the two files containing the partitions to be compared. Each line of a file is treated as a subset of the partition whose elements are stored as comma separated values. The module Text::CSV is used to parse each line. The files must in UTF-8 format.

The set of elements comprizing each partition must be equal to properly compare them. Set elements missing from either partition are added to the other partition as singleton subsets. For example, if fileP and fileQ contained the lines indicated below

fileP fileQ
----- -----
line 1 a,b,c a,b
line 2 d,e,f c,d
line 3 g,h

then the singleton sets {g} and {h} are added to partition P making it equal {{a,b,c}, {d,e,f}, {g}, {h}} and similarly, the sets {e} and {f} are added to Q making it equal {{a,b}, {c,d}, {e}, {f}, {g,h}}.